This link should clear that up:
https://www.government.nl/topics/c/coronavirus-covid-19/visiting-the-netherlands-from-abroad/mandatory-negative-test-results-and-declaration/rules-when-changing-planes
Specifically this part:
Just in case he would suddenly need a test for his stopover (which I doubt because of the information above), here you can see that one of the requirements is that it's not older than 48 hours before departure from, in this case, Brazil:
https://www.government.nl/topics/coronavirus-covid-19/visiting-the-netherlands-from-abroad/mandatory-negative-test-results-and-declaration/information-on-the-test-result
And considering he is going to take a test anyway, I would assume the stopover won't be a problem (mainly because a test is not required, the way I read it, but also because if it is, he will have what I assume is a valid one).